The present invention relates to spectrophotometers, and more particularly relates to a small-size integrated spectrophotometer.
Spectrophotometers are used in many analyzing apparatus such as an analyzing apparatus for biochemistry. Those spectrophotometers combining optical component parts have the problems of how to rectify shift in the positioning alignment between the optical component parts to improve wavelength accuracy and how to reduce size thereof. As a solution to these problems, a technique concerning one-chip spectrophotometer has been proposed in Japanese patent application laid-open No. 2001-340309 by the present applicant.
Shown in FIG. 1 is a disassembled perspective view of the small-size spectrophotometer as proposed in the above Japanese patent application laid-open No. 2001-340309. FIG. 1 includes: 101, Si substrate; 102, an optical waveguide formed by etching of Si substrate 101; 103, a light entrance slit formed on an indented end surface on Si substrate 101 of the optical waveguide 102; 104, a diffraction grating serving as optical element formed on an end surface of the optical waveguide 102 facing the light entrance slit 103; and 105, a photodiode array serving as photoelectric conversion device formed on the end surface of the optical waveguide 102 toward which the light entrance slit 103 is formed such that a portion of Si substrate 101 be the light receiving portion thereof. Here, the light entrance slit 103, the center of the diffraction grating 104, and the light receiving surface of each individual photodiode of the photodiode array 105 is disposed along the Rowland circle.
Further, a reflecting film of metal such as Al or Au is coated on a bottom surface 106 of the optical waveguide 102 to form a reflecting surface. Also, a reflecting film of metal such as Al or Au is thinly coated on the surface of the diffraction grating 104. What is denoted by numeral 107 is a board for sealing the optical waveguide 102, coated with a reflecting film 108 of metal such as Al or Au on the surface thereof facing the optical waveguide. The board 107 is then closely abutted against the Si substrate 101 to seal the optical waveguide 102 so as to form a spectrophotometer.
In thus constructed spectrophotometer, light entered through the light entrance slit 103 is reflected on and separated into a spectrum at the diffraction grating 104 as indicated by arrows 109 and is incident on the photodiode array 105. The signals obtained from the photodiodes are subjected to signal processing by an externally provided amplifier, signal processing circuit, etc. It should be noted that the light is introduced into the light entrance slit 103 by an optical fiber 110.
With the spectrophotometer constructed as the above, the following advantages are obtained. First, the accuracy of measurement is improved, since the light entrance slit, diffraction grating serving as optical element, and each photodiode of the photoelectric conversion device are disposed along the Rowland circle. Further, it can be readily manufactured by using semiconductor technologies, and an integrated forming of the optical waveguide, light entrance slit, diffraction grating and photodiodes is possible. In short, it can be formed on a single chip so as to be reduced in size. Furthermore, the efficiency in using light is improved, since the portion from the light entrance slit through the photoelectric conversion device is formed within the optical waveguide. Measurement without a loss of output from the photoelectric conversion device is then possible even when it is reduced in size. Moreover, the positioning adjustments for example between the optical components parts become unnecessary so that a reliable spectrophotometer can be achieved.